The present invention relates to an electronic device system for allowing component electronic devices to exchange data therebetween through a data interface pursuant to a predetermined data communication format; to a controlling device constituting part of such an electronic device system; and to a controlling method for use with the electronic device system.
Today, the IEEE (Institute of Electrical and Electronic Engineers) 1394 data interface has gained widespread acceptance as a digital data interface. Faster than the SCSI (Small Computer System Interface) among others in terms of data transfer rates, the IEEE 1394 data interface is known to permit isochronous communication whereby data of a predetermined size are transmitted and received periodically. As such, the IEEE 1394 data interface is deemed advantageous in transferring stream data such as AV (audio/video) data in real time.
Against that background, those AV systems have been proposed which interconnect various digital AV devices and electronic equipment such as a personal computer via a data bus complying with data interface standards such as the IEEE 1394.
One such AV system is a so-called component system which centers on an amplifier device and includes a CD player, an MD recorder/player, and various AV source output devices such as video equipment, all interconnected via a data bus within the system.
The above type of AV system allows commands to be exchanged between a plurality of its component devices in accordance with IEEE 1394 data interface criteria so that one device may control another device in what is known as a remote control operation. This feature helps make the AV system more functional and convenient.
Illustratively, with an IEEE 1394 data interface in use, the completion of a single command transmission process is defined as ranging from transmission of a command from a device acting as a controller to a device serving as a target, to reception by the controller of a final response from the target regarding the transmitted command. The process is called a transaction. According to IEEE 1394 criteria, the controller is prevented from initiating any new process such as transmission of a new command until the series of steps constituting a single transaction comes to an end.
Suppose now that the target which received a command may be slow in returning a final response illustratively because of an incomplete process it has undertaken since before the receipt of the command. In that case, the controller is forced to wait for the unfinished transaction to be completed, which may take some time.
Suppose also that a plurality of component devices making up the system are run cooperatively under remote control so as to accomplish a certain action. In that setup, the controller may require each of the target devices working in cooperation to carry out an independent transaction. If it takes some time to complete a transaction with each target, then an inordinately long time may have to elapse before all targets complete their cooperative operations. As a result, the user may feel frustrated at seeing the system operate in a very sluggish fashion in its cooperative action.